Wikipedia
GenesisIV
GenesisIV is a photorealistic landscape renderer program made by Geomantics Ltd. of Balquhidder, Scotland.
GenesisIV is similar to Terragen in that it uses an atmosphere lighting model, but differs in that this trades off some sophistication so that it can be implemented in hardware using OpenGL shaders. GenesisIV also places a stronger emphasis on landscape visualization for GIS and Educational use than for pure Computer Graphics.